Revert of Removed the ScriptedSpeech content side. (patchset #2 id:20001 of https://codereview.chromium.org/598923002/)

Reason for revert:
I'm sorry, the ENABLE_SPEECH_RECOGNITION switch is still used in the Chrome on
Android repo. I don't see (on the short term) another way of handling this than
not removing that switch. I'm going to revert this change.

Original issue's description:
> Removed the ScriptedSpeech content side.
>
> Removal the corresponding changes in blink are applied in the following patch
> https://codereview.chromium.org/599863002/
>
> BUG=402536
>
> Committed: https://crrev.com/6b8dda12a7d842517c5c4ee155cf48951e908a7f
> Cr-Commit-Position: refs/heads/master@{#296655}

TBR=avi@chromium.org,mohan.reddy@samsung.com
NOTREECHECKS=true
NOTRY=true
BUG=402536

Review URL: https://codereview.chromium.org/602083002

Cr-Commit-Position: refs/heads/master@{#296692}
5 files changed